Study on enhancing methods to 5.5kW total average power by combining YAG laser beams and their materials processing characteristics

摘要

We investigated firstly the welding characteristics with YAG laser beams transmitted though optical fibers and combined at a each focal point after a short consideration of combining methods of YAG laser beams. Each laser beam must be inclined in such a combined system. The plume and the penetration changed their direction from the vertical direction of the specimen to the parallel one of a irradiated beam, if the peak power or energy of the irradiated YAG laser beam exceed a threshold value. In the two cw YAG laser beams irradiation the form of plume and welding penetration were same at the inclined angle of 15° within our power level as those with a single and vertically irradiated beam to the specimen surface, but were splitted above the inclined angle of 30° and total average power of 3. 3kW. Two keyholes would be formed under the splitted penetration condition. The three splitted plumes were also observed at three beams irradiation. We developed secondly a integration optics based on these experiments, which could focus the laser beams transmitted through optical fibers with a condensing lens. We studied all position welding characteristics using the developed integration optics and obtained the result that the overhead welding has the maximum fusion volume among a horizontal, an vertical and an overhead position welding. The result will be attributed to the direct reach of laser beam to the unfused bottom metal due to the gravitational hanging down of molten metal around the keyhole. The integration optics is too heavy and large for an articulated robot to hand it and move with high speed. This difficulty comes from combining laser beams at the exit sides of optical fibers. Then, we developed a new launching optics of laser beams at an entrance side of an optical fiber in order to overcome the disadvantage. The development of the launching optics was described finally.